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Equity And Earnings Per Share (Diluted Table) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Diluted earnings per share:
Net income available for common stockholders	$ 41	$ 23	$ 87	$ 47
Weighted Average Shares Outstanding [Abstract]
Weighted Average Number of Shares Outstanding, Basic	72,476,729	69,087,853	71,979,104	68,539,526
Potentially dilutive common shares:
Issuable pursuant to employee incentive plans	852,767	975,574	944,640	1,074,041
Weighted Average Number of Shares Outstanding, Diluted	73,329,496	70,063,427	72,923,744	69,613,567
Earnings Per Share, Diluted	$ 0.57	$ 0.32	$ 1.20	$ 0.67
Common Class A
Weighted Average Shares Outstanding [Abstract]
Weighted Average Number of Shares Outstanding, Basic	72,476,629	69,087,753	71,979,004	68,539,426
Common Class B
Weighted Average Shares Outstanding [Abstract]
Weighted Average Number of Shares Outstanding, Basic	100	100	100	100

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Potentially Dilutive Common Shares [Abstract]

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The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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Amount, after deduction of tax, noncontrolling interests, dividends on preferred stock and participating securities, and addition from assumption of issuance of common shares for dilutive potential common shares; of income (loss) available to common shareholders.

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The sum of dilutive potential common shares or units used in the calculation of the diluted per-share or per-unit computation.

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